But the 28-member bloc is being deliberately vague about when they will come into force, to allow time to assess the implementation of a ceasefire agreed on Friday, BBC Europe correspondent Chris Morris reports.

"Depending on the situation on the ground, the EU stands ready to review the agreed sanctions in whole or in part," Mr van Rompuy said.

The ceasefire appears to be holding, although the head of the Organization for Security and Cooperation in Europe (OSCE), which brokered the deal, described it on Monday as "shaky".

Before the truce came into place, pro-Russian separatists made big gains in eastern Ukraine and seized territory a few miles outside the strategic south-eastern port city of Mariupol.

Image copyrightAFPImage caption
Mr Poroshenko delivered military awards as part of his visit to Mariupol

Image copyrightEPAImage caption
Ukrainian troops could be seen near the town of Kramatorsk on Monday

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Meanwhile in Donetsk, rebels held a ceremony to commemorate the struggle against the Nazis in World War Two

The gas sector is not affected by the latest sanctions. However, major state-owned oil firms are included, such as Rosneft, which is already targeted by US measures.

Russia has warned that it could block international flights through its airspace if the EU goes ahead with new measures.

Diplomats say the new package will target Russian oil companies Rosneft and Transneft and the petroleum unit of state gas monopoly Gazprom.

'Crushing defeat'

Also on Monday, Ukrainian President Petro Poroshenko said that pro-Russian rebels in Ukraine have released 1,200 prisoners.

The releases followed Friday's ceasefire deal, he said, which included an exchange of prisoners.

He was speaking during a visit to Mariupol, which has come under shelling from pro-Russian rebels in recent days.

Mr Poroshenko said during his visit on Monday that the city's defences would be reinforced and that rebels would suffer a "crushing defeat" if they advanced on the city.

Mariupol is the last city in Donetsk region still held by the Ukrainian government and is a strategic port on the route to Crimea, the peninsula annexed by Russia in March.

Fighting in eastern Ukraine has left some 2,600 people dead since April.

Media captionPetro Poroshenko: "We should have the representatives of the OSCE - just for the quick reaction if anything goes wrong"

Analysis: Andrew Walker, BBC economics correspondent

Rosneft calls itself the leader of the Russian petroleum industry. That makes it a very important player in the European Union's energy market. About 90% of the crude oil used in the EU is imported and Russia is, by a large margin, the biggest supplier.

The sanctions don't appear to directly affect that relationship. They would prevent Rosneft raising money in European financial markets.

But as crude oil is mainly transported by sea, if the trade were disrupted any losses from Russian suppliers could potentially be replaced. It would almost certainly be more expensive, but it could be done, up to a point.

Gas is another story, which may explain why Gazprom's main business is reported not to be on the new sanctions list. Russian gas is delivered to Europe by pipeline. There is a trade in gas transported by sea, but it would be very difficult to compensate for a major disruption of supplies from Russia.

The sanctions would also expand the visa bans and asset freezes on Russian officials and entities, including separatist leaders in Ukraine.